This invention relates to a lactic acid bacteria drink and a process for the production of the same. More particularly, it relates to a lactic acid bacteria drink, which is a fermentation product produced by kefir fungi in the form of a transparent refreshing drink and exerts an immunoinvigoration effect, and a process for the production of the same.
Kefir is a traditional milk fermentation drink which originates from the Caucasus in Central Asia and has been popularized over a wide area including Europe. Kefir is produced by adding an appropriate amount of activated Kefir grains or a Kefir starter to a milk (mainly cow's milk or mare's milk) and then allowing the milk to undergo fermentation at 15.degree. to 25.degree. C. for one to two days.
The term "kefir fungi" as used herein means a natural symbion of various microorganisms which behave as a single organism from a biological viewpoint. The kefir fungi are generally provided as lyophilized or water-immersed kefir grains as large as an adzuki bean to the head of a little finger in the form of a white cauliflower. These kefir grains are inoculated usually into a milk medium and repeatedly cultured therein. The activated kefir grains thus obtained or the culture medium may be employed as a kefir starter.
The fermentation with the kefir fungi is mainly caused by lactic acid bacteria and yeasts originating from the kefir grains or the kefir starter. Namely, lactic acid fermentation is observed first, followed by yeast fermentation.
In the production of kefir, the full performance of the lactic acid fermentation and the yeast fermentation requires a prolonged fermentation time. In this case, furthermore, it is difficult to maintain well-balanced fermentation under the influence of other contaminating microorganisms. Thus this process is unsuitable for industrial production.
The yeast fermentation imparts a mellow flavor to the fermentation product which is never observed in common yoghurts. However the over fermentation, which occurs during the storage, causes the separation of whey, the excessive yeast odor and gassing, thus deteriorating the properties of the product.
On the other hand, it is difficult at present to sterilize or pasteurize the product so as to solve the above-mentioned problems caused by the over fermentation in order to stabilize the product.
This is because the fermentation product contains a large amount of casein protein, which makes it difficult to directly sterilize it by filtering. When the product is to be thermally pasteurized, a large amount of a sugar or a stabilizer should be added in order to prevent the agglutination of curd. These additives are liable to affect the viscosity or taste of the fermentation product, which might deteriorate the characteristic flavor of the kefir.
Japanese patent application Kokai publication No. 63-146748 proposed a process for the production of kefir free from these disadvantages. In this process, a whey component, to which a yeast flavor achieved by fermentation has been imparted, is pasteurized or sterilized and then mixed with a fermented milk. Thus a fermented milk product or a kefir-like product having a mellow flavor and a high stability can be obtained.
In the case of kefir, however, this process suffers from such problems that the yeast flavor is weakened or an increase in the solid milk content lowers the refreshness.
Meanwhile as regards the physiological activities of kefir, there have been reported an immunoinvigoration effect and an antithrombotic effect caused by polysaccharides. It is reported that the kefir fermentation product would exert similar effects.
However the extends and intensities of these effects vary from report to report. It is generally believed that the oral intake of kefir would bring about only limited effects and unstable reproduction.